Solar control coatings having a layer stack of glass/Si3N4/NiCr/Si3N4 are known in the art, where the metallic NiCr layer is the sole infrared (IR) reflecting layer in the coating. In certain instances, the NiCr layer may be nitrided. For example, see U.S. Pat. No. 6,926,967, which is hereby incorporated herein by reference. See also U.S. Pat. No. 5,688,585.
Unfortunately, while such layer stacks with NiCr IR reflecting layers provide efficient solar control and are overall good coatings, they are lacking in terms of being able to achieve a wider palette of available colors when desired. For example, with such a coating stack, if bluish green is desired the approach is to significantly increase the bottom dielectric thickness which unfortunately results in undesirable interference effects in that particular coating.
Blue coloration is often desired in the context of monolithic windows, insulating glass (IG) window units, and/or other suitable applications. Desirable blue coloration (e.g., glass side/exterior/outside reflective), measured monolithically and/or in an IG window unit, may be characterized by: b* values of from −8.0 to −30.0, more preferably from −11.0 to −19.0, and most preferably −12.0 to −18.0; optionally in combination with a* values of from −7.0 to +7.0, more preferably from −5.0 to +5.0, and most preferably from −3.0 to +2.0.
Low solar factor (SF) and solar heat gain coefficient (SHGC) values are also desired in some applications, particularly in warm weather climates. Solar factor (SF), calculated in accordance with EN standard 410, relates to a ratio between the total energy entering a room or the like through a glazing and the incident solar energy. Thus, it will be appreciated that lower SF values are indicative of good solar protection against undesirable heating of rooms or the like protected by windows/glazings. A low SF value is indicative of a coated article (e.g., IG window unit) that is capable of keeping a room fairly cool in summertime months during hot ambient conditions. Thus, low SF values are sometimes desirable in hot environments. While low SF values are sometimes desirable for coated articles such as IG window units, the achievement of lower SF values may come at the expense of sacrificing coloration. It is often desirable, but difficult, to achieve a combination of acceptable visible transmission, desirable glass side reflective coloration, and a low SF value for a coated article such as an IG window unit or the like. SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculated from the full spectrum (T, Rg and Rf) and are typically measured with a spectrophotometer such as a Perkin Elmer 1050. The SF measurements are done on monolithic coated glass, and the calculated values can be applied to monolithic, IG and laminated applications.
U.S. Patent Document 2012/0177899 discloses several different coatings. Examples 1-5 on page four of US '899 are glass/SiN/NiCrNx/SiN/NiCrNx/SiN. However, none of these examples achieve blue glass side reflective coloration, as evidenced by their respective glass side reflective (b*G) values outside of the range from −8 to −30. Moreover, these examples suffer from undesirably high SF and SHGC values.
U.S. Pat. No. 8,286,395 discloses numerous coatings, but none can accomplish the features of coatings according to embodiments of this invention. The coatings in Comparative Example 1 of US '395 cannot achieve blue glass side reflective color, as evidenced by their respective glass side reflective (a*G/external) values outside of the range of from −8 to −30. The coating of Comparative Example 2 in US '395 has an undesirably green film side color as evidenced by the a*F/internal value of −4.8. And the counter-examples under Comparative Example 2 in US '395 are undesirable in that they have high glass side visible reflectivity values of 22.6% and 21.2%, respectively. Coating Nos. 1-2 in Comparative Example 3 of US '395 are undesirable in that neither can achieve blue glass side reflective coloration as evidenced by their respective glass side reflective (a*G/external) values outside of the range of from −8 to −30, and Coating No. 1 also has an undesirably high glass side visible reflectance (RYG/out) of 28%. Under Example 3 of US '395, coating No. 3 is undesirable in that it requires additional titanium (Ti) metal layers, and coating No. 4 has an undesirably high glass side visible reflectance (RYG/out) of 22.3% as well as an undesirably green film side reflective color as evidenced by the a*F/internal value of −11.3. Thus, it will be appreciated that coatings of US '395 cannot achieve desirable blue glass side reflective coloration in combination with low glass side visible reflectivity, acceptable film side coloration, and a low solar factor (SF) and/or low solar heat gain coefficient (SHGC). US '395 is silent as to SF and SHGC values. It is noted that glass side reflective color is a significant color when an IG window unit is provided with the coating on surface two, as the glass side reflective color is the color seen by those outside viewing the building on which the window is mounted.
It would be desirable if blue glass side reflective coloration could be achieved in an efficient manner in combination with low glass side visible reflectivity, acceptable film side coloration, and a low solar factor (SF) and/or low solar heat gain coefficient (SHGC). Note that a typical conventional IG window unit with two panes has an SHGC value around 0.70.
In certain example embodiments of this invention, it has surprisingly been found that by providing two or more IR reflecting layers (e.g., of or including NbZr and/or NbZrNx) between respective dielectric layers, along with particular thickness parameters, desirable blue glass side reflective coloration can be achieved in combination with low glass side visible reflectivity, acceptable film side coloration, and a low solar factor (SF) and/or low solar heat gain coefficient (SHGC). Such coatings provide for improved color control and/or ranges when desired, low SF values and thus the ability to keep rooms cool in warm climates, and also for good thermal stability (low ΔE* value(s)) if desired.
Generally speaking, certain example embodiments of this invention fulfill one or more of the above listed needs by providing a coated article having blue glass side reflective coloration and including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer comprising nitrogen; a first infrared (IR) reflecting layer on the glass substrate over at least the first dielectric layer; a second dielectric layer comprising nitrogen on the glass substrate over at least the first dielectric layer and the first IR reflecting layer; a second layer IR reflecting layer on the glass substrate over at least the second dielectric layer; a third dielectric layer comprising nitrogen on the glass substrate over at least the second IR reflecting layer; wherein each of the first and second IR reflecting layers comprises one or more of: NbZr, NbZrNx, NiCr, NiCrNx, NiCrMo, NiCrMoNx, NbCr, NbCrNx, Nb and NbNx; wherein the coated article contains no metallic infrared (IR) reflecting layer based on Ag and/or Au, and wherein the IR reflecting layers do not physically contact any other metallic or substantially metallic layer; and wherein the coated article: has glass side visible reflectance of no greater than 18%, a film side/interior reflective a* color value of −2 to +12, glass side/exterior reflective blue coloration comprising a glass side/exterior b* color value of from −8.0 to −30.0; and (i) if measured monolithically has an SF value of no greater than 0.35 and an SHGC value of no greater than 0.40, and/or (ii) if an insulating glass (IG) window unit having two glass substrates has an SF value of no greater than 0.25 and an SHGC value of no greater than 0.27.
In certain example embodiments of this invention, there is provided a coated article having blue glass side reflective coloration and including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer comprising silicon nitride; a first infrared (IR) reflecting layer comprising NbZr on the glass substrate over at least the first dielectric layer comprising silicon nitride; a second dielectric layer comprising silicon nitride on the glass substrate over at least the first dielectric layer comprising silicon nitride and the first IR reflecting layer comprising NbZr; a second layer IR reflecting layer comprising NbZr on the glass substrate over at least the second dielectric layer comprising silicon nitride; a third dielectric layer comprising silicon nitride on the glass substrate over at least the second IR reflecting layer comprising NbZr; wherein the coated article contains no metallic infrared (IR) reflecting layer based on Ag and/or Au, and wherein the IR reflecting layers do not physically contact any other metallic or substantially metallic layer; and wherein the coated article: has glass side visible reflectance of no greater than 18%, a film side/interior reflective a* color value of −2 to +12, glass side/exterior reflective blue coloration comprising a glass side/exterior b* color value of from −8.0 to −30.0; and (i) if measured monolithically has an SF value of no greater than 0.35 and an SHGC value of no greater than 0.40, and/or (ii) if an insulating glass (IG) window unit having two glass substrates has an SF value of no greater than 0.25 and an SHGC value of no greater than 0.27.
Thus, this invention covers monolithic window units, IG window units, laminated window units, and any other article including a glass substrate having a coating thereon as claimed. Note that monolithic measurements may be taken by removing a coated substrate from an IG window unit and/or laminated window unit, and then performing monolithic measurements. It is also noted that for a given coating the SF and SHGC values will be significantly higher for a monolithic window unit than for an IG window unit.
In certain example embodiments of this invention, heat treated (HT) coated articles have a glass side reflective ΔE* value due to heat treatment (e.g., thermal tempering) of no greater than 4.5, more preferably no greater than 4.0, even more preferably no greater than 3.5, and most preferably no greater than 3.0. For purposes of example, the heat treatment (HT) may be for at least about 5 minutes at a temperature(s) of at least about 580 degrees C., and is sufficient for thermal tempering. The term ΔE* is known in the art and is indicative of thermal stability upon heat treatment, and is defined and explained for example in U.S. Pat. No. 6,926,967 which is incorporated herein by reference.